The advantages of using a self-supporting molded construction form in the building industry are well known in the art. These construction forms are manufactured from a polymeric material, often polyurethane or polystyrene, which expands within a mold to yield a rigid, low-density foamed plastic form having vertical and/or horizontal cavities to be filled with wet concrete. The polystyrene concrete forms typically have a tongue and groove arrangement on all sides to allow for the interlocking placement of additional forms on either side, above, and below a form as to construct a solid wall or structure. Wet concrete is poured into the construction forms which are then left in place, instead of being removed, once the concrete has cured thereby providing support for the concrete and insulation for the finished building structure. U.S. Pat. No. 3,552,076, entitled "CONCRETE FORM" to Gregori, and U.S. Pat. No. 3,788,020, entitled "FOAMED PLASTIC CONCRETE FORM WITH FIRE RESISTANT TENSION MEMBER" to Gregori both teach methods whereby polystyrene foam is molded to yield a concrete form.
The construction industry has incorporated several means of attaching finishing materials to the outer sides of these molded construction forms after the concrete within the cavities has set. One such method has been to glue the paneling, sheetrock, or other suitable finishing materials to the outer surfaces of the completed form. .Additionally, outer finishing materials may be rigidly attached using a penetrating device through the outer molded form to the dried concrete or other building material inside the form. Another method to attach finishing materials is to glue or nail furring strips on the outer surfaces of the forms. Gluing the furring strips to the foam forms require construction adhesive, and nailing the furring strips or the finishing materials to the outer sides of the forms require that special concrete nails be used. The application of these concrete nails, moreover, must be accomplished at a critical time during the curing of the concrete. Then, the finishing materials are nailed or screwed onto the furring strips.
Another method whereby materials can be mounted to a building structure has been to glue an intermediate attachment surface to the outer surface of a polymeric building structure. The adhesion of sheet metal to polyester foam beams is presented in U.S. Pat. No. 3,922,828, entitled "STRUCTURAL MEMBER" to Patton. Finishing materials are then attached by means of nails or screws to the strips of sheet metal. The disadvantages associated with this arrangement is that it is costly and time consuming to apply a continuous sheet of metal to the outer surfaces of building studs or beams. Moreover, adhesion materials are also costly and the adhesion may eventually deteriorate with the resultant separation of the finishing materials from the synthetic structural member. An alternative embodiment of the Patton invention is to embed a Z-shaped piece of steel within the polyester structural beam and to attach the finishing material to the outer surfaces with screws or other penetrating devices through the Z-shaped steel member. This means of attachment poses the difficulty of locating the steel members embedded within the structure and do not extend to the outer surfaces. A large piece of steel is required to either cover large building beams or studs, or to embed the steel within the beam or stud. This not only makes the beam or stud heavy and burdensome, but it is costly to provide such a large piece of steel in the structure.
Another method for applying materials particularly to the concrete form previously discussed is presented in U.S. Pat. No. 4,223,501, entitled "CONCRETE FORM" to DeLozier. This patent teaches a method whereby a one piece transverse connecting member is embedded in the polystyrene concrete form taught in the Greqori patent. The connecting member has attachment flanges extending at right angles which extend near the outer surfaces of the form, and thus are allegedly suitable for receiving fastening members penetrating the flanges. The disadvantages presented by the DeLozier invention include the difficulty of locating the flanges once the concrete form is in place and the concrete has been poured because the attachment flanges are positioned below the outer surface of the concrete forms. The DeLozier invention teaches that the attachment flanges can be located with either a template or markings on the foam units. Alternatively, the attachment flanges can be located by breaking away the foam to reveal the flanges for attachment. All of the above methods are time consuming and require additional labor.
The manufacturing costs associated with the concrete form embodied in the DeLozier patent, moreover, are high partially because of the one piece construction of the connecting members and extending flanges. The connecting member taught by DeLozier is manufactured from heavy gage steel with arcuate or polygonal holes punched in the steel, thus generating substantial waste material. The one piece construction of the connecting member and the attachment flanges, furthermore, requires that the attachment flanges be made from the same heavy gage steel as the connecting member. Practical application of the DeLozier invention reveals that it is difficult to screw or attach finishing materials to the form because the steel is too thick. The DeLozier invention uses only two of these connecting members per form unit wherein each connecting member is placed midway between the center and the edges of the form presumably because of the cost of the steel and the weight of the heavy gage steel used. The use of only two connecting members per form does not practicably yield additional strength or reinforcement of the concrete form at the weakest parts of the form which are the ends.
A device similar to the invention taught by DeLozier has been in use in the industry incorporating a metal connecting member, but the attachment flanges are pieces of wood, generally of a 2.times.2 size, embedded in the outer surfaces of the concrete form. The wooden flanges are stapled to the metal connecting member, and then the finishing materials such as sheetrock is attached to the wood as is common in the art. Two wooden attachment members are used on each outer surface of the polystyrene concrete form, and are located midway between the center and the ends of the forms. This arrangement presents several disadvantages, some of which have already been discussed. First, the use of the wooden attachment members at the two locations provides no reinforcement of the construction form at the weakest parts of the form, i.e., the ends of the form. Secondly, it is impossible to apply these wooden attachment flanges to the ends of the form because they interfere with the tongue and groove arrangement for the fitting of adjacent forms. Lastly, the stapling of the wood flanges to the central metal web portion presents a point of potential failure. The wood may easily separate from the metal web portion and, at worse, the finishing materials could separate from the outer surfaces of the construction forms.
A construction panel unit made up of solid flanges and expanded steel mesh is taught in U.S. Pat. No. 3,872,636, entitled "LIGHT WEIGHT LOAD BEARING METAL STRUCTURAL PANEL" to Nicosia. This unit is intended to provide for high strength compression and tension load sustaining surfaces in the construction of walls, ceilings, floors and the like, and is used in place of the molded construction form. It would be impossible to apply this construction panel to a molded construction form without having new molds machined to accommodate the elaborate configuration of steel mesh and steel bars embodied in the Nicosia invention. Rather, the panel presents a construction alternative to the molded construction form. The cost of fabrication of this panel, moreover, is relatively high compared to the cost of the polystyrene construction forms incorporating the features of the present invention.